The present invention relates to a power steering apparatus, and is preferably applicable to an electric power steering apparatus for assisting the steering force using the rotation force of an electric motor.
As the power steering apparatus, an oil pressure power steering apparatus and an electric power steering apparatus are available.
In the oil pressure type power steering apparatus as disclosed in Japanese Utility Model Kokai Publication No. Hei. 6-78156, a valve mechanism is formed between an input axis and an output axis, and a so-called valve stopper by which the relative rotation of the input axis and output axis is regulated to a predetermined angle, is provided. Because this valve stopper is arranged in the oil in an engine room, a sound of collision of the valve stopper is hardly heard by the driver.
On the one hand, in the case of the electric power steering apparatus in which the steering assistant force is generated by an electric motor provided in a column as disclosed in Japanese Utility Model Kokoku Publication No. Hei. 8-1466, the stopper to regulate the relative rotation of the input axis and the output axis is arranged in a car room. Accordingly, when the steering wheel is turned maximum, for example, at the time of parking, the stopper impact sound is transmitted to the driver as a rasping sound. Accordingly, it is considered that a cushioning material, such as rubber, is provided at a stopper portion between the input axis and the output axis, however, a space is narrow, and actually, the layout is difficult. Further, even when the cushioning material is arranged, only a cushioning material having the small impact absorption capacity can be arranged, and the durability is decreased.
In view of the foregoing problems, the present invention is attained, and an object of the present invention is to provide an power steering apparatus by which the generation of the impact sound at the time of steering at parking is greatly decreased.
The present invention is directed to a power steering apparatus in which a steering assistant force for driving a steering mechanism is generated in accordance with a relative displacement between an input shaft and an output shaft connected to each other through a torsion bar.
The power steering apparatus comprises:
a first stopper mechanism located between the input shaft and the output shaft, the first stopper mechanism including a pair of mating contact portions contactable with each other to regulate a relative rotation between the input shaft and the output shaft within a predetermined range; and
a second stopper mechanism provided at each end of the steering mechanism, the second stopper mechanism including a pair of mating contact members contactable with each other to regulate a movement of a sliding shaft in the steering mechanism.
In the power steering apparatus, at least one of the contact members includes an elastic member, and when the sliding shaft is moved to a stroke end, the second stopper mechanism is operated and thereafter the first stopper mechanism is operated.
When the steering wheel is turned maximum at the time of parking, the second stopper mechanism including the elastic member provided outside the car room is operated earlier, i.e., before the first stopper mechanism arranged in the car room is operated. Since the contact members including the elastic member contact with each other, the impact is fully absorbed. That is, the strike speed when contact portions contact with each other, is relieved, or the contact itself can be avoided in some cases. Accordingly, the generation of the uncomfortable noise in the car room due to the strike sound of the first stopper mechanism can be prevented.
The present disclosure relates to the subject matter contained in Japanese patent application No. Hei. 11-339533 (filed on Nov. 30, 1999), which is expressly incorporated herein by reference in its entirety.